For example, Japanese Unexamined Patent Application Publication No. 2004-332876 discloses a two-port solenoid valve that opens and closes an elongate output orifice by using a slender tabular solenoid-operated valve member in the same manner as a poppet valve. In this solenoid valve, when an exciting coil is energized, the valve member is attracted to a fixed core and the output orifice is opened. When the energization is stopped, the valve member is separated from the fixed core by the action of fluid pressure and is pressed against a valve seat disposed around the output orifice. Thus, the output orifice is closed.
Such a solenoid valve having the above-described structure has an excellent responsiveness due to having a short stroke for opening and closing the valve member, but a further improvement in the responsiveness has been required in recent years.
Since the operating force with which the valve member opens the valve seat is electromagnetic force, the responsiveness during opening of the valve can be improved with relative ease by enhancing the electromagnetic force. However, since the operating force with which the valve member closes the valve seat is fluid pressure, the responsiveness during closing of the valve is extremely difficult to improve. The responsiveness can be improved by further shortening the stroke of the valve member, but the flow rate of the pressurized fluid is disadvantageously reduced with the stroke.